a 1/2 + 1/4 + 3/4
on met sur /4
a 2/4 + 1/4 +3/4 = 6/4 =3 /2
b 1/3 + 2/3 = 3/3 = 1
c 1/2 + 1/3 + 1/4
on met sur /12
c 6/12 + 4/12 + 3/12 = 13/12
d 2/3 + 3/4
/d 8/12 + 9/12 = 17/12
